The Axial Skeleton

Skeletal system includes both:

• Axial skeleton

• Skull

• Auditory ossicles and hyoid bone

• Vertebral column

• Thoracic cage

• Appendicular skeleton

• Pectoral and pelvic girdles

• Upper and lower limbs

The skull

• Consists of the cranium and the bones of the face

• The cranium encloses cranial cavity

• Facial bones surround and protect the entrances to the respiratory and digestive tracts

• Superficial landmarks include the sutures

• Lambdoid

• Coronal

• Sagittal

• Squamous

Focus: The Individual Bones of the Skull Cranial Bones

• one occipital bone

• foramen magnum

• two parietal bones

• one frontal bone

• frontal sinuses

The Axial Skeleton

Facial bones

• Maxillary bones

• Mandible

• Palatine bones

• Nasal bones

• Vomer

Maxillae

• Largest facial bones

• Form the upper jaw and most of the hard palate

Palatine and Nasal Bones

• Palatine bones

• Small “L” shaped bones

• Form the posterior hard palate and floor of the nasal cavity

• Nasal bones

• Superior border of external nares

Vomer, Zygomatic and Lacrimal bones

• Vomer

• Inferior portion of the nasal septum

• Zygomatic bone

• Temporal process articulates with zygomatic process of temporal bone

• Lacrimal bones

• Smallest bones of the face

• Sit medially in orbit

Mandible and Hyoid bones

• Mandible

• Bone of the lower jaw

• Hyoid

• Suspended by stylohyoid ligaments

• Supports the larynx

The orbital and nasal complexes

• Seven bones in the orbital complex

• Nasal complex = bones that enclose the nasal cavities and paranasal sinuses

Skulls of infants and children

• Fontanels permit skulls of infants and children to continue growing

Vertebral column

• Vertebrae, sacrum, coccyx

• 7 cervical vertebrae

• 12 thoracic vertebrae

• 5 lumbar vertebrae

• Sacrum and coccyx are fused vertebrae

Spinal curvature

• Four spinal curves

• Primary (accommodation) curves = thoracic and sacral

• Secondary (compensation) curves = lumbar and cervical

Vertebral anatomy

• Typically has a body and vertebral arch

• Superior and inferior articular processes

• Separated by intervertebral discs

Vertebral regions

• Cervical

• Has distinctive shape

• Large relative size of vertebral foramen

• Costal processes with transverse foramina

• Notched spinous processes

Thoracic vertebrae

• Heart-shaped body

• Long slender spinous processes

• Articulations for ribs

Lumbar vertebrae

• Most massive

• Least mobile

• Subjected to great stresses

Sacrum

• Protects reproductive, digestive and urinary organs

• Articulates with pelvic girdle and fused elements of coccyx

Thoracic cage

• Thoracic vertebrae

• Ribs

• Sternum

• Ribs and sternum forms the rib cage

The ribs

• Ribs 1-7 are attached to vertebrae

• 8-12 are vertebrochondral ribs

• 11-12 are floating ribs

Typical rib

• Has a head, neck, tubercle and a body

• Costal groove marks pathway of blood returning to the heart

The Sternum consists of

• Manubrium

• Body

• Xiphoid process